Nothing specific but one could say it was implicit as part of the speed modifications - especially as the Kelvans had their ship entirely destroyed by the barrier one would assume they'd be concerned about it. The only other time the Enterprise hit the barrier it turned around so it's hard to say if a Constitution class could do it without modification.
From transcript at http://www.chakoteya.net/StarTrek/50.htm
Captain's log, stardate 4657.5. Work is proceeding on the Enterprise as my crew is forced to make the required changes in the ship for intergalactic travel. I can't forget the picture of Yeoman Thompson crushed to a handful of dust
Edit: It may be worth noting that the Warp 11 of the TOS cubed formula is roughly TNG warp 9. So when the Excelsior was set to break some classic speed records...perhaps Starfleet learned something from the events of this episode. Anything above Warp 8 should be concerning on the TOS scale.